I. Field of the invention
The present invention relates to a facsimile machine for printing on single sheets, comprising an ink-jet printing head which is movable along a printing line and may be activated to print on a copy sheet, and a line feed device mounted upstream of the printing line to make each sheet advance in front of the printing line.
II. Related Art
Facsimile machines with ink-jet printing devices are very advantageous because of the high print quality which may be obtained, the low cost of the sheets of ordinary paper used for the copies, and the unalterability of the copies. These machines have technical problems, of which some problems relate to the adaptation of the ink-jet device to the facsimile, while other problems are also common in ink-jet printers in general use. In the case of a facsimile, the problems of the printers are more serious, owing to the constraints of size, cost and reliability which are typical of facsimile machines.
The ink-jet heads form printing lines consisting of minuscule ink droplets which remain wet for a few seconds after they have been fixed to the copy sheet. The advance of the single sheet is effected by gripping parts of the line feed device which engage the two sides of a sheet to draw it in front of the head to a collecting station. The gripping parts are necessarily disposed upstream of the printing line to prevent them from coming into contact with the ink which is still wet, which would cause the lines to smudge and would cause staining of other parts of the copy sheet. This arrangement prevents the sheet from being advanced incrementally in the section in the space between the printing line and the gripping parts of the advance device. This makes it impossible to form lines of print adjacent to the trailing edge of the single sheet.
A technical problem of the present invention is that of providing a facsimile machine for single sheets with an ink-jet head, in which it is possible to form printing lines adjacent to the trailing edge of a single sheet.
The printing devices used in facsimile machines are generally derived from printing mechanisms for general use. In these printing mechanisms, in order to avoid smudges and stains due to the still-wet ink in the course of printing, the single sheets are collected by a copy holding frame which is opened only after the whole sheet has been completely printed. The sheet may thus be laid on top of the other previously printed sheets in the collecting station without any sliding of the non-printed side of the last sheet with respect to the printed side of the penultimate sheet.
In a known printer, the frame is opened by substantially vertical control levers by the side of the collecting station. This structure produces a printing mechanism which is rather high, and this is not acceptable in a facsimile machine of the compact type.
The printing head comprises ink ejection nozzles which are kept free from obstructions in a cleaning station controlled by suitable activation means. This station also generally provides a protective cap for the ejection nozzles, cap displacement means which may be activated to make the cap adhere to the needles, and a pump to apply a reduced pressure to the needles and suck ink residues from the protective cap.
In facsimile machines or ink-jet printers of the known type, independent means are provided for the control of the opening of the copy holding frame, and for the activation of the cleaning station, including the control of the cap displacement and the pump actuation. This makes the machine expensive.